Electrode mounting for electrical discharge lamps, and particularly for discharge lams with fluorescent screens



Feb. 9, 1954 2,668,928

ROGER FRANCOIS DESIRE NAVARRE (DIT MALHERBE) ELECTRODE MOUNTING FOR ELECTRICAL DISCHARGE LAMPS, AND PARTICULARLY FOR DISCHARGE LAMPS WITH FLUORESCENT SCREENS Filed May 11, 1950 I 17 van for 7?. F17. Na Var/e 0 27 Ma/Aerbc Patented Feb. 9, 1954 UNITED STATES FATENT OFFICE ELECTRODE MOUNTING FOR ELECTRICAL DISCHARGE LAMPS, AND PARTICULARLY FOR DISCHARGE LAMPS WITH FLUORES- CENT SCREENS Belgium Application May 11, 1950, Serial No. 161,368

Claims priority, application France May 21, 1949 1 4 Claims.

The present invention relates to electrical discharge lamps in a gas or metallic vapor, particularly to discharge lamps with fluorescent screens or fluorescent lamps and more particularly to the means for starting such discharge lamps.

The problem of starting electrical discharge lamps is a complex problem both with respect to the operation of the lamp itself as well as to the auxiliary apparatus attached thereto.

A good starting requires observing all the necessary conditions on this subject and particularly those relating to the voltage applied as a function of the distance between the electrodes and the pressure of the gas filling the interior of the lamp. It also requires taking into account the conditions for preserving the lamp and in particular the electrodes and the auxiliary apparatus. It is also desirable to satisfy these conditions with the aid of an installation as economical as possible.

Various methods have already been proposed for starting electrical discharge lamps which give more or less satisfaction. Among these the following may be noted:

a. Those which comprise a preheating of the electrodes of the lamp.

b. Those which bring about by way of resonance an electrical supervoltage between the lamp electrodes.

0. Those which comprise starting an auxiliary discharge between auxiliary electrodes carried at a suitable potential and the main electrodes of the lamp.

When an electrical discharge lamp is provided with auxiliary electrodes, an auxiliary starting device may be constructed comprising shunts upon a single source of current supply, a circuit for placing the main electrodes under tension, an electrical stabilization apparatus inserted in the circuit of the main electrodes and impedances located in the circuit of the auxiliary electrodes in order to feed the latter from the circuit of the main electrodes, said impedances being capable of creating by the resonance effect with the fundamental component or any harmonic component of the circuit for placing under tension the main electrodes of the lamp a sufficient electrical supervoltage for starting an auxiliary discharge. Such discharge will bring about the starting of the discharge at the interior of the lamp between the main electrodes.

If the operation of the lamp is observed the discharge between the main electrodes is therefore carried out in two stages:

a. Ihe main electrodes being cold thermionic emission takes place first by luminescent discharge with the auxiliary electrodes. The reduced dimension of the main electrodes or of the portion of the latter nearest the auxiliary electrodes brings about a first rapid elevation of the temperature of the main electrodes or of a portion of the latter up to a value useful for thermionic emission.

1). Under the electronic emission so produced the ionization of the gas or of the metallic vapor in the main circuit determines in its turn the starting of the discharge as a function of the number of electrons emitted by the main electrodes. The temperature continues to rise progressively under the effect of the impact of the accelerated positive ions in the fall of the potential or" the cathodic field up to the value limited by the intensity controlled by the electrical stabilization apparatus of the lamp.

After starting the electrical discharge between the main electrodes, the auxiliary paths may be eliminated in order to cancel their electrical consumption as well as for improving cathodic pulverization of the auxiliary electrodes. It has resulted from experience that such a pulverization towards the main electrodes forms upon the latter a deposit which can be so important as to conceal, thin out and then cancel the thermionic emission. This will reduce the length of life of an electrical discharge lamp considerably.

An object of the invention is to provide certain arrangements for the mounting of the auxiliary electrodes whereby the length of life of electrical discharge lamps may be increased by eliminating or limiting the cathodic pulverizetion of the auxiliary electrodes.

A further object of the invention is to provide electrode mountings for electrical discharge lamps and particularly for discharge lamps with fluorescent screens having together or separately the following features:

a. The auxiliary electrode is located at the side opposed to the discharge path with respect to the corresponding main electrode and the density of the surface current of the auxiliary electrode is very small of the order of 0.0005 to 0.001 ampere per square centimeter.

b. The auxiliary electrode is formed from a metal of low ionizing potential such as aluminum, magnesium, the alloys of these metals or alkaline metals.

0. One or more screens of an insulating material are located in the path of the auxiliary discharge.

d. One or more metallic screens which may be insulated or connected to a suitable potential are located in thepath of the auxiliary discharge.

e. The auxiliary electrodes may be of a geometrical form having an axis of revolution centered upon the corresponding mainelectrode such, for example, as superposed annular discs, a cylinder having a smooth, corrugated or deformed side wall or a cylinder provided with interior and/or exterior wings or fins.

f, The discharge between a main electrode-and the auxiliary electrode cooperating therewith is of the opposed discharge"typ'e.

The disadvantages of the cathodic pulverization are eliminated or limited in the invention by the use of a. Auxiliary electrodes permitting low density of surface current.

b. Metals of low ionizing potential permitting with equal density, a considerably reduced operating temperature and voltage drop'compa'red to the usual metals used.

With the above and other objects in view which will appear from the detailed descriptionsome forms of electrode mountings according to the invention which are given by way of example are shown in the drawingsin which:

Fig. 1 is a cross-sectional view of an auxiliary electrode having a plurality of superposed annular discs'spaced from one another.

Fig. 2 ise plan-view of-theauxiliary electrode shown in Fig. 1.

Fig.3 is a cross-sectional view of amodification showing the auxiliary electrode inthe form ofa cylinder with a corrugated side wall with the main electrode locatedat the axis'of suchc'ylinder.

Fig. 4 is a plan view of theelectrodes shown in Fig. 3.

Fig. 5 is'a cross-sectional view of'a further modification wherein the auxiliary electrode is in the form of a cylinder having interior fins.

Fig. 6 is a plan view of the auxiliary electrode shown inFig. 5.

Fig. '7 is a cross-sectional view of "a further modificationwherein in addition to the auxiliary electrode shown in Fig. 1 there is provided a screen,

Fig. -8 is a cross-sectionalviewillustratingla still further modification wherein a screen of insulating material is provided.

In the various views similar reference characters indicate like parts.

Referring to the form of the invention shown in Figs. 1 and 2, l is the foot at "one end of an electrical'discharge lamp and 2 is the protecting casing for the-current inlets. The main electrode is shown'at-3 and 4 indicates the lead-ins for the current of the main electrode.

The auxiliary electrode is illustrated at 5 and the lead-in for such auxiliary electrode is shown at 6. In this modification the auxiliary electrode is constructed with a plurality of superposed annular discs located at a spaced distance from one another.

In the modification shown in Figs. 3 and 4 the auxiliary electrode 5' is constructed in' the form of a cylinder having corrugations 20 in the side walls thereof as clearly shown in Fig. 4. The main electrode 3 is located at the axis of the cylinder 5.

The auxiliary electrode 5" of the modification shown in Figs. 5 and 6 is in the form of a cylinder having interior .fins 1. The main electrode is located at theaxis of the cylinder 5".

The modification shown in Fig. 7 is similar to "the form shown in Fig. 1 but in addition has located above the auxiliary electrode 5 a metallic screen 8 which maybe polarized or nonpolarized. The screen =8 is'connected to the lead-in 9 and is designed 'to intercept and neutralize the projections. In this form of the invention the screen is inthe form of an annular disc havin substantially the same dimensions as one of the disc's forming'the auxiliary electrode '5.

In the modification shown in Fig. 8, the screen In is a metallic screen not connected to a source of current -or 'is a screen of insulating material such asmica or steatite. This screen is also located in the path of the projections.

It' is thought that the invention and its advantages will be understood from the foregoing description and it is apparent that various changes may be made in the:form, construction and arrangement'of the parts without departing from the spirit and scope of the invention or sacrificing its material advantages, the forms hereinbefore described and illustrated inthe drawings being merely preferred embodiments thereof.

I claim:

1. An electrode mounting 'for electrical discharge lampscomprising principal and auxiliary electrodes and particularly for fluorescent lamps which are started by means of ionizing auxiliary electrical discharges which heat the-principal electrodes, wherein (a) theauxiliary electrode is constituted of a metal of a low ionization-potential, (b) the density of the surface current of the auxiliary electrode is of the order of 00005170 0.001 ampere per square centimeter; c) the auxiliary electrode is located at the-side opposite to the principal electrical discharge path with respect to the principal electrode, and "(d-) the discharges between the principal a electrode and the auxiliary electrode are of the opposeddischarge type.

2. A relationship of parts 'according to clalm 1, wherein a screen of insulating material is located in the path of the auxiliary discharges between the principal and auxiliary electrodes.

3. A relationship of parts accordingto claim 1, wherein an electrically insulated metalli'c screen is located in the path of the auxiliary discharges between the principal and auxiliary electrodes.

4. A relationship of parts according'to'claim l,'wherein-a metallic screen is located in the path of the auxiliary dischargesbetween the principal and auxiliary electrodes; said screen being adapted to'be connected to a source of electrical potential.

ROGER FRANCOIS DESIRE 'NAVARRE DIT 'MALHERBE.

References Cited in the file of this patent 1 UNITED STATES PATENTS Number Name Date 1,267,199 Ferguson May 21, 1918 2,028,548 Kirsten Jan. 21, 1936 [2,034,572 Found Mar. 17, 1936 2,038,049 Kirsten Apr. '21, 1936 2,103,052 Wiegand Dec. 21, 1937 21173208 Lecorguillier Sept. 19, 1939 

